This invention relates to a novel catalyst component to be employed with a cocatalyst for use in the polymerization of olefins to polyolefins such as polyethylene, polypropylene and the like and especially in the production of high density and linear low density polyethylene, copolymers such as ethylene copolymers with other alpha-olefins and diolefins, which catalyst component shows unusually high activity and excellent hydrogen response for the control of polymer molecular weight while obtaining improved comonomer response and improved bulk density. The polymer product obtained evidences an important balance of polymer properties, for example, the catalyst system obtains a polymer with good bulk density, a narrow molecular weight distribution and an improved balance in polymer product machine direction tear strength and transverse direction tear strength. As a result, for example, the blown film produced from LLDPE manifests an overall high strength.
The catalyst component comprises a solid reaction product obtained by contacting a solid, particulate, porous support material such as, for example, silica, alumina, magnesia or mixtures thereof, for example, silica-alumina, in stages with a transition metal compound, an organometallic composition treated with an alcohol, an acyl halide and a Group IIIa metal hydrocarbyl dihalide. The novel catalyst component, which when used with an aluminum alkyl cocatalyst, provides the novel catalyst system of this invention which can be usefully employed for the polymerization of olefins.
The catalyst system can be employed in slurry, single-phase melt, solution and gas-phase polymerization processes and is particularly effective for the production of linear polyethylenes such as high density polyethylene and linear low density polyethylene.
Recently, interest has arisen in the use of magnesium-titanium complex catalyst components for the polymerization of olefins. For example, European Patent Application No. 27733, published Apr. 29, 1981 discloses a catalyst component obtained by reducing a transition metal compound with an excess of organomagnesium compound in the presence of a support such as silica and thereafter deactivating the excess organomagnesium compound with certain deactivators including hydrogen chloride.
U.S. Pat. No. 4,136,058 discloses a catalyst component comprising an organomagnesium compound and a transition metal halide compound, which catalyst component is thereafter deactivated with a deactivating agent such as hydrogen chloride. This patent des not teach the use of support material such as silica but otherwise the disclosure is similar to the above-discussed European patent application.
U.S. Pat. No. 4,250,288 discloses a catalyst which is the reaction product of a transition metal compound, an organomagnesium component and an active non-metallic halide such as HCl and organic halides containing a labile halogen. The catalyst reaction product also contains some aluminum alkyls.
Catalyst components comprising the reaction product of an aluminum alkyl-magnesium alkyl complex plus titanium halide are disclosed in U.S. Pat. No. 4,004,071 and U.S. Pat. No. 4,276,191.
U.S. Pat. Nos. 4,173,547 and 4,263,171, respectively disclose a catalyst component comprising silica, an organoaluminum compound, titanium tetrachloride and dibutyl magnesium and a catalyst component comprising a magnesium alkyl-aluminum alkyl complex plus titanium halide on a silica support.
Each of U.S. Pat. Nos. 4,402,861, 4,378,304, 4,388,220, 4,301,029 and 4,385,161 disclose supported catalyst systems comprising an oxide support such as silica, an organomagnesium compound, a transition metal compound and one or more catalyst component modifiers. These patents do not disclose the catalysts of this invention.
In British No. 2,101,610 silica is treated with a magnesium alkyl, an alcohol, benzoyl chloride and TiCl.sub.4. In each of Japanese Kokai No. 50-098206 and 57-070107 acyl halides are employed during the preparation of titanium supported catalysts.
The catalyst systems comprising magnesium alkyls and titanium compounds, although useful for the polymerization of olefins such as ethylene and other 1-olefins, often do not show excellent responsiveness to hydrogen during the polymerization reaction for the control of molecular weight, do not readily incorporate comonomers such as butene-1 for the production of ethylene copolymers, do not show an extremely high catalytic activity and obtain polymer product manifesting poor bulk density and film properties which are unbalanced under anisotropic conditions.
In U.S. Pat. No. 4,451,574 issued May 29, 1984 a catalyst system obtained by treating an inert particulate support, such as silica, with an organometallic compound, a titanium halide and a halogen gas is disclosed. Although the catalyst obtains very high activities, there is a need for improving the film properties of polymer product obtained by polymerizing olefins in the presence of the catalyst and to improve the bulk density of polymer product.
In accordance with this invention catalyst combinations have been found which have extremely high catalytic activities and excellent hydrogen responsiveness for the control of molecular weight and obtain polymer product with greatly improved film properties and bulk density. The resins exhibit excellent melt strength with a surprising decrease in power consumption hence an increase in extrusion rates, as well as excellent MD tear strength in excess of 80 g/mil and dart impact strength in excess of 70 g/mil with a 1.0 dg/min and 0.918 g/cc density film.
The new catalyst systems and catalyst component of this invention are obtained by contacting an organometallic compound, an alcohol, an acyl halide, a transition metal compound and a Group IIIa metal hydrocarbyl dihalide in the presence of a oxide support. The catalyst system employing the transition metal containing catalyst component is advantageously employed in a gas phase ethylene polymerization process since there is a significant decrease in reactor fouling as generally compared with catalytic prior art ethylene gas phase polymerization processes thereby resulting in less frequent reactor shut downs for cleaning.